2-Isopropylbenzimidazole and 2-methylbenzimidazole as bulky proton sources: Stereoselective protonation and application to the synthesis of γ- and δ-lactones

Aakash Sengupta, Seijiro Hosokawa

    Research output: Contribution to journalArticle

    1 Citation (Scopus)

    Abstract

    2-Isopropylbenzimidazole and 2-methylbenzimidazole have been found to be effective bulky proton sources for stereoselective protonation of chiral enolate anions. 2-Isopropylbenzimidazole worked in the stereoselective protonation of the Birch reduction of chiral α,β-unsaturated imides. On the other hand, 2-methylbenzimidazole was found to be the best protonation reagent in the isomerization reaction of α,β-unsaturated imide into β,γ-unsaturated imide. The Birch reduction using 2-isopropylbenzimidazole realized a concise and stereoselective synthesis of δ-lactone 14, a sex pheromone of Macrocentrus grandii, while the isomerization reaction using 2-methylbenzimidazole was employed in the highly stereoselective synthesis of the γ-lactone intermediate in the synthesis of depsipeptide antibiotics. These bulky proton sources would be powerful tools to achieve a concise synthesis of natural products.

    Original languageEnglish
    Pages (from-to)411-414
    Number of pages4
    JournalTetrahedron Letters
    Volume60
    Issue number5
    DOIs
    Publication statusPublished - 2019 Jan 31

    Keywords

    • Benzimidazole
    • Proton source
    • Stereoselective protonation
    • γ-Lactone
    • δ-Lactone

    ASJC Scopus subject areas

    • Biochemistry
    • Drug Discovery
    • Organic Chemistry

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